//
//  CCamera.cpp
//  OpenGLDemo
//
//  Created by 石超军 on 2018/7/6.
//  Copyright © 2018年 石超军. All rights reserved.
//
#include <glad/glad.h>
#include "CCamera.h"

// Constructor with vectors
CCamera::CCamera(glm::vec3 position , glm::vec3 up , float yaw , float pitch)
: Front(glm::vec3(0.0f, 0.0f, -1.0f)), MovementSpeed(SPEED), MouseSensitivity(SENSITIVITY), Zoom(ZOOM)
{
    Position = position;
    WorldUp = up;
    Yaw = yaw;
    Pitch = pitch;
    UpdateCameraVectors();
}
// Constructor with scalar values
CCamera::CCamera(float posX, float posY, float posZ, float upX, float upY, float upZ, float yaw, float pitch)
: Front(glm::vec3(0.0f, 0.0f, -1.0f)), MovementSpeed(SPEED), MouseSensitivity(SENSITIVITY), Zoom(ZOOM)
{
    Position = glm::vec3(posX, posY, posZ);
    WorldUp = glm::vec3(upX, upY, upZ);
    Yaw = yaw;
    Pitch = pitch;
    UpdateCameraVectors();
}

// Returns the view matrix calculated using Euler Angles and the LookAt Matrix
glm::mat4 CCamera::GetViewMatrix()
{
    return glm::lookAt(Position, Position + Front, Up);
}

// Processes input received from any keyboard-like input system. Accepts input parameter in the form of camera defined ENUM (to abstract it from windowing systems)
void CCamera::ProcessKeyboard(Camera_Movement direction, float deltaTime)
{
    float velocity = MovementSpeed * deltaTime;
    if (direction == FORWARD)
        Position += Front * velocity;
    if (direction == BACKWARD)
        Position -= Front * velocity;
    if (direction == LEFT)
        Position -= Right * velocity;
    if (direction == RIGHT)
        Position += Right * velocity;
    if (direction == UP)
        Position += Up * velocity;
    if (direction == DOWN)
        Position -= Up * velocity;
}

// Processes input received from a mouse input system. Expects the offset value in both the x and y direction.
void CCamera::ProcessMouseMovement(float xoffset, float yoffset, GLboolean constrainPitch)
{
    xoffset *= MouseSensitivity;
    yoffset *= MouseSensitivity;
    
    Yaw   += xoffset;
    Pitch += yoffset;
    
    // Make sure that when pitch is out of bounds, screen doesn't get flipped
    if (constrainPitch)
    {
        if (Pitch > 89.0f)
            Pitch = 89.0f;
        if (Pitch < -89.0f)
            Pitch = -89.0f;
    }
    
    // Update Front, Right and Up Vectors using the updated Euler angles
    UpdateCameraVectors();
}

// Processes input received from a mouse scroll-wheel event. Only requires input on the vertical wheel-axis
void CCamera::ProcessMouseScroll(float yoffset)
{
    if (Zoom >= 1.0f && Zoom <= 45.0f)
        Zoom -= yoffset;
    if (Zoom <= 1.0f)
        Zoom = 1.0f;
    if (Zoom >= 45.0f)
        Zoom = 45.0f;
}

// Calculates the front vector from the Camera's (updated) Euler Angles
void CCamera::UpdateCameraVectors()
{
    // Calculate the new Front vector
    glm::vec3 front;
    front.x = cos(glm::radians(Yaw)) * cos(glm::radians(Pitch));
    front.y = sin(glm::radians(Pitch));
    front.z = sin(glm::radians(Yaw)) * cos(glm::radians(Pitch));
    Front = glm::normalize(front);
    // Also re-calculate the Right and Up vector
    Right = glm::normalize(glm::cross(Front, WorldUp));  // Normalize the vectors, because their length gets closer to 0 the more you look up or down which results in slower movement.
    Up    = glm::normalize(glm::cross(Right, Front));
}
